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                <a name="asio.reference.basic_datagram_socket.cancel.overload2"></a><a class="link"
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                                                                                       title="basic_datagram_socket::cancel (2 of 2 overloads)">basic_datagram_socket::cancel
                (2 of 2 overloads)</a>
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    <p>
        <span class="emphasis"><em>Inherited from basic_socket.</em></span>
    </p>
    <p>
        Cancel all asynchronous operations associated with the socket.
    </p>
    <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">cancel</span><span
            class="special">(</span>
    <span class="identifier">asio</span><span class="special">::</span><span class="identifier">error_code</span> <span
                class="special">&amp;</span> <span class="identifier">ec</span><span class="special">);</span>
</pre>
    <p>
        This function causes all outstanding asynchronous connect, send and receive
        operations to finish immediately, and the handlers for cancelled operations
        will be passed the <code class="computeroutput"><span class="identifier">asio</span><span
            class="special">::</span><span class="identifier">error</span><span class="special">::</span><span
            class="identifier">operation_aborted</span></code>
        error.
    </p>
    <h6>
        <a name="asio.reference.basic_datagram_socket.cancel.overload2.h0"></a>
        <span><a name="asio.reference.basic_datagram_socket.cancel.overload2.parameters"></a></span><a class="link"
                                                                                                       href="overload2.html#asio.reference.basic_datagram_socket.cancel.overload2.parameters">Parameters</a>
    </h6>
    <div class="variablelist">
        <p class="title"><b></b></p>
        <dl>
            <dt><span class="term">ec</span></dt>
            <dd><p>
                Set to indicate what error occurred, if any.
            </p></dd>
        </dl>
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        <a name="asio.reference.basic_datagram_socket.cancel.overload2.h1"></a>
        <span><a name="asio.reference.basic_datagram_socket.cancel.overload2.remarks"></a></span><a class="link"
                                                                                                    href="overload2.html#asio.reference.basic_datagram_socket.cancel.overload2.remarks">Remarks</a>
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    <p>
        Calls to <code class="computeroutput"><span class="identifier">cancel</span><span
            class="special">()</span></code>
        will always fail with <code class="computeroutput"><span class="identifier">asio</span><span
            class="special">::</span><span class="identifier">error</span><span class="special">::</span><span
            class="identifier">operation_not_supported</span></code>
        when run on Windows XP, Windows Server 2003, and earlier versions of
        Windows, unless ASIO_ENABLE_CANCELIO is defined. However, the CancelIo
        function has two issues that should be considered before enabling its
        use:
    </p>
    <div class="itemizedlist">
        <ul class="itemizedlist" type="disc">
            <li class="listitem">
                It will only cancel asynchronous operations that were initiated in
                the current thread.
            </li>
            <li class="listitem">
                It can appear to complete without error, but the request to cancel
                the unfinished operations may be silently ignored by the operating
                system. Whether it works or not seems to depend on the drivers that
                are installed.
            </li>
        </ul>
    </div>
    <p>
        For portable cancellation, consider using one of the following alternatives:
    </p>
    <div class="itemizedlist">
        <ul class="itemizedlist" type="disc">
            <li class="listitem">
                Disable asio's I/O completion port backend by defining ASIO_DISABLE_IOCP.
            </li>
            <li class="listitem">
                Use the <code class="computeroutput"><span class="identifier">close</span><span
                    class="special">()</span></code>
                function to simultaneously cancel the outstanding operations and
                close the socket.
            </li>
        </ul>
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    <p>
        When running on Windows Vista, Windows Server 2008, and later, the CancelIoEx
        function is always used. This function does not have the problems described
        above.
    </p>
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